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monoflo system

jhansen
jhansen Member Posts: 59
We recently removed an old national boiler from a home built in 1874. Somewhere along the line it was converted to a monoflo system keeping the large upright radiators. We installed a Weil McLain CGa boiler and now all but one radiator is not heating. It is on the first floor with a run equal to the other radiators. The new boiler got a taco 007 as was on the old boiler. We proceeded to flush the radiator both ways with a hose and backwards to the monoflo tee. No luck. Could the added resistance of the new boiler have pushed us beyond a 007 pump?

Comments

  • icesailor
    icesailor Member Posts: 7,265
    Non-working Monoflows:

    Something else is wrong. It's not the circulator. A 007 is supposed to be a direct replacement for a B&G Series 100 and the Mono0flow "one pipe" systems all worked on them.

    Post photos of the boiler and near piping.

    You either have an obstruction or a circulator that isn't pumping.
  • JStar
    JStar Member Posts: 2,752
    Monoflo

    The Taco is not a "direct" replacement. It has slightly different characteristics than the B&G. It sounds like you might have air in the one radiator that isn't working.
  • Ironman
    Ironman Member Posts: 6,555
    Possibly...

    Are you certain it's a mono-flow system? If so, it could just be a matter of bleeding all the air out. Mono-flows can be difficult to bleed. Start at the rad closest to the boiler and bleed it first. Close the valve on it once it's bled and then on to the next one til all are done. Then open all the valves and start the boiler.



    If the old pipes are large, then you may need to look at a larger circ. I always pipe p/s when there are large pipes in the old system.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • jhansen
    jhansen Member Posts: 59
    monoflo problems

    Thank you for responding. This picture doesnt show much. But the other 8 radiators are heating fine. We cut into the supply and return to the radiator and flushed both ways.
  • JStar
    JStar Member Posts: 2,752
    edited October 2012
    Boiler

    Deleted
  • Ironman
    Ironman Member Posts: 6,555
    Split Return?

    It appears from the pic that you have a split return. To bleed it properly, you'll have to close off one side at a time. Then you may need to do some balancing between each side.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • jhansen
    jhansen Member Posts: 59
    monoflo system

    Venting the radiator we just shut down pump and bled from coin vent on radiator. Im sure its not air. And yes it is a monoflo system. Rest of the house heats great. This radiator is on the old back porch.
  • JStar
    JStar Member Posts: 2,752
    Radiator

    Do you have any pictures of the radiator and a gneral layout of piping legnths from the main supply?
  • Ironman
    Ironman Member Posts: 6,555
    Did it heat before?

    If so, then it may be that you need to try a larger circ like a ups15-58 on hi speed.

    I'd try closing off the other side of the split return and see if it works then. If so, then you know the circ doesn't have enough velocity with the large piping.

    How far apart are the Tee's on the offending rad? How long are the run outs? Can you post a pic of it?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • jhansen
    jhansen Member Posts: 59
    monoflo system

    Bob,

    That makes sense. I appreciate the input from everyone. Have a great day.
  • icesailor
    icesailor Member Posts: 7,265
    One radiator not heating:

    A 007 will work fine on that system.

    The circuits should have been split into two zones because it is already split.

    If the radiator in the back that doesn't work now, worked before. it may have long lines with air somewhere and you won't vent it out. Raise the system pressure to 20# or more and leave it there for a day or so. It will compress the air and maybe let the water circulate. This happened to me recently and raising the pressure solved the problem overnight.
  • icesailor
    icesailor Member Posts: 7,265
    One radiator not heating:

    A 007 will work fine on that system.

    The circuits should have been split into two zones because it is already split.

    If the radiator in the back that doesn't work now, worked before. it may have long lines with air somewhere and you won't vent it out. Raise the system pressure to 20# or more and leave it there for a day or so. It will compress the air and maybe let the water circulate. This happened to me recently and raising the pressure solved the problem overnight.
  • JStar
    JStar Member Posts: 2,752
    edited October 2012
    Air

    Just don't let the burners run in that condtiion or you could blow the relief valve. You may be better off raising the water temperature a few extra degrees to make the water more buoyant, allowing it to rise to all of the radiators with any trapped air. You can then bleed them out. Conversely, by lowering the temperature, you may move any air along through the system to an air vent. May or may not work, but it's quick and easy.
  • icesailor
    icesailor Member Posts: 7,265
    Confused:

    I'm now confused.

    Do all the radiators work except one?

    Or do none of the radiators work but one and only one radiator gets hot?

    It has always been my experience and understanding that a radiator, connected at the bottom with a supply and a return, will heat whether full or half full. The half full radiator only gets hot up to the level where the water and air meet.

    It has always been my experience that when you get water out of a cast iron radiator that is connected with a supply and return on the bottom, will always get hot is=f the circulator is pumping and the water if flowing through the system. I drain and fill a lot of old houses (winterize) with radiators. I always fill and vent from the top down. I can feel the heated water as it rises inside the columns.

    It has also been my understanding that under-pumped mono-flows work better than over pumped mono-flows. That over-pumped mono-flows may not flow at all. But I must say that I have never seen a system that was so over-pumped that it didn't work. And I've never seen a mono-flow system that didn't work if properly installed. I;ve never used anything other than a 007 since I switched from B&G Series 100 or Taco 110's.
  • duffy_4
    duffy_4 Member Posts: 72
    Monoflow system

    Recently did boiler replacement on a split monoflow system here in Chicago ,one rad on second floor wouldn't heat found that original monoflow tee galv 1 1/2 by 1/2 was to close to the regular tee ,repiped it with correct distance between tees ,bled it and worked great,also check pitch of pipes off the tees if dipped they can hold air and prevent flow.
  • Jason_13
    Jason_13 Member Posts: 299
    Broken monoflo system

    Verify the water is going in the right direction. Arrow on circulator and tees should be the same direction. Tees should be on the return side of the connected radiation. Tees should not be closer than 18" between the supply and return monoflo tee. A better rule of thumb is the same distance between the tees and the length of the radiation connected to the tees. Supply tee and return tee to the same radiator should not have any other tees between them to another radiator. Better air elimination by moving the pump to the supply pumping away from the expansion tank connection.

    Taco 007 may not be big enough. Each 1-1/4" monoflo tee is equal to 23 ft of pipe dependent on tee size. If this radiator not heating is the last one on the loop it may just be a flow issue. How much water do you have to move? heat loss/10,000 gives you gpm required. Slow down flow and get less heat, too much resistance equals slower flow. 
  • Stet
    Stet Member Posts: 22
    Mono Flow Problem

    FIRST, make sure that (if the radiator is above the loop) that both the supply and return are pitching UP to the radiator. You can fill the radiator full of water, but if the lines are not pitched right and you get any kind of air pocket, it won't heat. I do find this to be a problem once in a while when the complete system has been drained.. The loop in the basement might have been rehung and the pipe to that radiator might be pitching wrong.



    I don't believe the problem is the pump. Other than that, make sure that the mono flow tee didn't get partially plugged. Most of the time, it been a pitch problem.
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